Ethylene-tetrafluoroethylene (ETFE) copolymers have a wide variety of useful applications. They have good structural strength, a relatively high melting temperature, and excellent chemical, electrical and high energy radiation resistance properties. ETFE has good structural durability and heat resistance, having a tensile strength of 6100 psi (42 N mm−2), with a working temperature range of −184° C. to +150° C.
ETFE is an excellent material both as the jacketing and primary insulator of electrical cables. Because of its properties ETFE can be used in high stress and high reliability situations. This includes, but is not limited to, aircraft and spacecraft wiring.
The resistance of ETFE to heat and abrasion can be further improved by crosslinking the copolymer. The crosslinking is achieved in various ways. The highest levels of heat and abrasion resistance are achieved by crosslinking by adding a crosslinking agent and irradiating the ETFE copolymer with high-energy ionizing radiation. Unfortunately, during the crosslinking process, hydrogen fluoride (HF) gas is released. Hydrogen fluoride is highly corrosive, and readily damages wiring and other metallic parts. Irradiation with high-energy ionizing radiation releases high concentrations of HF from the ETFE copolymer. Attempts have been made to subject the crosslinked ETFE coated wire cable to a heat treatment to drive the HF off the coating. However, to date these efforts have proven ineffective. There is a long-felt need in the art for a way to reduce the amount of residual HF in crosslinked ETFE after crosslinking with high-energy ionizing radiation.